/**
 * https://tc39.es/ecma402/#sec-bestavailablelocale
 * @param availableLocales
 * @param locale
 */
export function BestAvailableLocale(availableLocales, locale) {
    var candidate = locale;
    while (true) {
        if (availableLocales.has(candidate)) {
            return candidate;
        }
        var pos = candidate.lastIndexOf('-');
        if (!~pos) {
            return undefined;
        }
        if (pos >= 2 && candidate[pos - 2] === '-') {
            pos -= 2;
        }
        candidate = candidate.slice(0, pos);
    }
}